The present invention relates generally to formation testing in subterranean wells and, in an embodiment described herein, more particularly provides a method and system for open hole formation testing.
Open hole formation testing is well known in the art. Typically, compression-set or inflatable packers are used to straddle a formation intersected by an uncased wellbore, and formation fluid is drawn from the formation into a test string extending to the earth""s surface. Generally, the formation fluid is flowed to the surface, where it may be sampled, tested, etc.
Because of safety and environmental concerns with flowing the formation fluid to the surface, it would be advantageous to be able to perform formation testing without flowing the formation fluid to the surface. The formation fluid should be flowed only into the test string, and then flowed back (i.e., re-injected) into the formation from which it originated, or into another disposal formation.
Unfortunately, satisfactory methods and systems for accomplishing such a formation test in an open hole environment have not yet been developed. Therefore, it would be highly advantageous to provide systems and methods whereby a formation test may be performed in an uncased wellbore, and without flowing formation fluid to the surface.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, systems and methods for open hole testing are provided. The systems and methods utilize a fluid barrier reciprocably received within an apparatus and displaceable when fluid is flowed between the apparatus and a formation. Other systems and methods are provided, as well.
In one aspect of the invention, a method of performing a test on a formation intersected by a wellbore is provided. The method includes the steps of installing a test apparatus in the wellbore, flowing fluid from the formation into the apparatus and applying pressure to the apparatus, thereby forcing the formation fluid to flow back into the formation from which it originated.
The test apparatus includes a fluid barrier reciprocably displaceable within the apparatus. The barrier has first and second opposite sides. The barrier displaces in a first direction in the apparatus as the formation fluid flows into the apparatus.
When pressure is applied to the apparatus on the second side of the barrier, the barrier displaces in a second direction opposite to the first direction. The formation fluid is forced by the applied pressure to flow back into the formation from which it originated.
In another aspect of the invention, a system for performing a test on a formation intersected by a wellbore is provided. The system includes at least one packer interconnected as part of an apparatus positioned in the wellbore, a fluid barrier reciprocably displaceable within the apparatus when fluid is flowed between the apparatus and the formation, and a module interconnected to the packer, the module alternately permitting and preventing setting and unsetting of the packer in response to reciprocal displacements of the barrier.
In yet another aspect of the invention, a system for performing a test on a formation intersected by a wellbore is provided. The system includes a fluid barrier reciprocably displaceable within an apparatus into which fluid from the formation is flowed, the barrier displacing when the formation fluid is flowed between the apparatus and the formation, and a valve in the apparatus, the valve being operated in response to displacement of the barrier.
In still another aspect of the invention a system for performing a test on a formation intersected by a wellbore is provided. The system includes a formation testing apparatus including at least one waste chamber and at least two packers configured for straddling the formation when set in the wellbore, the waste chamber being opened after the packers are set in response to pressure in an annulus formed between the apparatus and the wellbore.
Where there are multiple formations intersected by the wellbore to be tested, there may be a corresponding number of waste chambers. A module of the apparatus opens one of the waste chambers in sequence prior to each of the formations being tested.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.